In order to regulate the flow of fluid in a hydraulic system it is known to provide a flow regulating valve having inlet and outlet ports connected in the line and having a slidable valve element cooperating with the ports to define a variable flow passage therebetween, the rate of fluid flow depending upon the position of the valve element with respect to the ports. The valve element is normally biassed in a direction tending to close the variable flow passage and is displaceable against its bias to open the flow passage by a selected amount. For controlling the displacement of the valve element a pilot valve may be employed for supplying a control fluid to a pilot chamber on one side of the valve element, the positioning of the element being determined by the pilot chamber pressure and the force exerted by the biasing means.